Change: Use "bridge ... too low" message for bridgeable objects (#15838)

Depots are somewhat tall, so bridges must be at least 3 height levels above them.

src/depot_type.h

@@ -17,4 +17,7 @@ struct Depot;
 
 static const uint MAX_LENGTH_DEPOT_NAME_CHARS = 32; ///< The maximum length of a depot name in characters including '\0'
 
+/** Minimal height for a bridge above any depot tile. */
+static constexpr uint8_t MINIMAL_DEPOT_BRIDGE_HEIGHT = 3;
+
 #endif /* DEPOT_TYPE_H */

src/lang/english.txt

@@ -5361,6 +5361,10 @@ STR_ERROR_BRIDGE_TOO_LOW_FOR_BUOY                               :bridge is {HEIG
 STR_ERROR_BRIDGE_TOO_LOW_FOR_RAIL_WAYPOINT                      :bridge is {HEIGHT} too low for rail waypoint
 STR_ERROR_BRIDGE_TOO_LOW_FOR_ROAD_WAYPOINT                      :bridge is {HEIGHT} too low for road waypoint
 STR_ERROR_BRIDGE_TOO_LOW_FOR_LOCK                               :bridge is {HEIGHT} too low for lock
+STR_ERROR_BRIDGE_TOO_LOW_FOR_TRAIN_DEPOT                        :bridge is {HEIGHT} too low for train depot
+STR_ERROR_BRIDGE_TOO_LOW_FOR_ROADVEH_DEPOT                      :bridge is {HEIGHT} too low for road vehicle depot
+STR_ERROR_BRIDGE_TOO_LOW_FOR_SHIP_DEPOT                         :bridge is {HEIGHT} too low for ship depot
+STR_ERROR_BRIDGE_TOO_LOW_FOR_OBJECT                             :bridge is {HEIGHT} too low for object
 
 # Tunnel related errors
 STR_ERROR_CAN_T_BUILD_TUNNEL_HERE                               :Can't build tunnel here...

src/object_cmd.cpp

@@ -313,10 +313,11 @@ CommandCost CmdBuildObject(DoCommandFlags flags, TileIndex tile, ObjectType type
 
 	/* Finally do a check for bridges. */
 	for (TileIndex t : ta) {
-		if (IsBridgeAbove(t) && (
-				!spec->flags.Test(ObjectFlag::AllowUnderBridge) ||
-				(GetTileMaxZ(t) + spec->height >= GetBridgeHeight(GetSouthernBridgeEnd(t))))) {
-			return CommandCost(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
+		if (IsBridgeAbove(t)) {
+			if (!spec->flags.Test(ObjectFlag::AllowUnderBridge)) return CommandCost(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
+
+			int height_diff = GetTileMaxZ(t) + spec->height - GetBridgeHeight(GetSouthernBridgeEnd(t));
+			if (height_diff > 0) return CommandCostWithParam(STR_ERROR_BRIDGE_TOO_LOW_FOR_OBJECT, height_diff * TILE_HEIGHT_STEP);
 		}
 	}
 
@@ -1011,11 +1012,11 @@ static CommandCost TerraformTile_Object(TileIndex tile, DoCommandFlags flags, in
 static CommandCost CheckBuildAbove_Object(TileIndex tile, DoCommandFlags flags, [[maybe_unused]] Axis axis, int height)
 {
 	const ObjectSpec *spec = ObjectSpec::GetByTile(tile);
-	if (spec->flags.Test(ObjectFlag::AllowUnderBridge) && GetTileMaxZ(tile) + spec->height <= height) {
-		return CommandCost();
-	}
+	if (!spec->flags.Test(ObjectFlag::AllowUnderBridge)) return Command<Commands::LandscapeClear>::Do(flags, tile);
 
-	return Command<Commands::LandscapeClear>::Do(flags, tile);
+	int height_diff = GetTileMaxZ(tile) + spec->height - height;
+	if (height_diff > 0) return CommandCostWithParam(STR_ERROR_BRIDGE_TOO_LOW_FOR_OBJECT, height_diff * TILE_HEIGHT_STEP);
+	return CommandCost();
 }
 
 /** TileTypeProcs definitions for TileType::Object tiles. */

src/rail_cmd.cpp

@@ -1006,7 +1006,10 @@ CommandCost CmdBuildTrainDepot(DoCommandFlags flags, TileIndex tile, RailType ra
 		cost.AddCost(Command<Commands::LandscapeClear>::Do(flags, tile));
 		if (cost.Failed()) return cost;
 
-		if (IsBridgeAbove(tile)) return CommandCost(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
+		if (IsBridgeAbove(tile)) {
+			int height_diff = GetTileMaxZ(tile) + MINIMAL_DEPOT_BRIDGE_HEIGHT - GetBridgeHeight(GetSouthernBridgeEnd(tile));
+			if (height_diff > 0) return CommandCostWithParam(STR_ERROR_BRIDGE_TOO_LOW_FOR_TRAIN_DEPOT, height_diff * TILE_HEIGHT_STEP);
+		}
 
 		if (!Depot::CanAllocateItem()) return CMD_ERROR;
 	}
@@ -2582,7 +2585,7 @@ static void DrawTile_Rail(TileInfo *ti)
 		if (HasRailCatenaryDrawn(GetRailType(ti->tile))) DrawRailCatenary(ti);
 
 		DrawRailTileSeq(ti, dts, TransparencyOption::Buildings, relocation, 0, pal);
-		/* Depots can't have bridges above so no blocked pillars. */
+		blocked_pillars = BRIDGEPILLARFLAGS_ALL;
 	}
 	DrawBridgeMiddle(ti, blocked_pillars);
 }
@@ -3172,10 +3175,13 @@ static CommandCost TerraformTile_Rail(TileIndex tile, DoCommandFlags flags, int
 }
 
 /** @copydoc CheckBuildAboveProc */
-static CommandCost CheckBuildAbove_Rail(TileIndex tile, DoCommandFlags flags, [[maybe_unused]] Axis axis, [[maybe_unused]] int height)
+static CommandCost CheckBuildAbove_Rail(TileIndex tile, [[maybe_unused]] DoCommandFlags flags, [[maybe_unused]] Axis axis, int height)
 {
 	if (IsPlainRail(tile)) return CommandCost();
-	return Command<Commands::LandscapeClear>::Do(flags, tile);
+
+	int height_diff = GetTileMaxZ(tile) + MINIMAL_DEPOT_BRIDGE_HEIGHT - height;
+	if (height_diff <= 0) return CommandCost();
+	return CommandCostWithParam(STR_ERROR_BRIDGE_TOO_LOW_FOR_TRAIN_DEPOT, height_diff * TILE_HEIGHT_STEP);
 }
 
 /** TileTypeProcs definitions for TileType::Rail tiles. */

src/road_cmd.cpp

@@ -1166,7 +1166,10 @@ CommandCost CmdBuildRoadDepot(DoCommandFlags flags, TileIndex tile, RoadType rt,
 		cost.AddCost(Command<Commands::LandscapeClear>::Do(flags, tile));
 		if (cost.Failed()) return cost;
 
-		if (IsBridgeAbove(tile)) return CommandCost(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
+		if (IsBridgeAbove(tile)) {
+			int height_diff = GetTileMaxZ(tile) + MINIMAL_DEPOT_BRIDGE_HEIGHT - GetBridgeHeight(GetSouthernBridgeEnd(tile));
+			if (height_diff > 0) return CommandCostWithParam(STR_ERROR_BRIDGE_TOO_LOW_FOR_ROADVEH_DEPOT, height_diff * TILE_HEIGHT_STEP);
+		}
 
 		if (!Depot::CanAllocateItem()) return CMD_ERROR;
 	}
@@ -1884,7 +1887,7 @@ static void DrawTile_Road(TileInfo *ti)
 			}
 
 			DrawRailTileSeq(ti, dts, TransparencyOption::Buildings, relocation, 0, palette);
-			/* Depots can't have bridges above so no blocked pillars. */
+			blocked_pillars = BRIDGEPILLARFLAGS_ALL;
 			break;
 		}
 	}
@@ -2657,10 +2660,13 @@ CommandCost CmdConvertRoad(DoCommandFlags flags, TileIndex tile, TileIndex area_
 }
 
 /** @copydoc CheckBuildAboveProc */
-static CommandCost CheckBuildAbove_Road(TileIndex tile, DoCommandFlags flags, [[maybe_unused]] Axis axis, [[maybe_unused]] int height)
+static CommandCost CheckBuildAbove_Road(TileIndex tile, [[maybe_unused]] DoCommandFlags flags, [[maybe_unused]] Axis axis, int height)
 {
 	if (!IsRoadDepot(tile)) return CommandCost();
-	return Command<Commands::LandscapeClear>::Do(flags, tile);
+
+	int height_diff = GetTileMaxZ(tile) + MINIMAL_DEPOT_BRIDGE_HEIGHT - height;
+	if (height_diff <= 0) return CommandCost();
+	return CommandCostWithParam(STR_ERROR_BRIDGE_TOO_LOW_FOR_ROADVEH_DEPOT, height_diff * TILE_HEIGHT_STEP);
 }
 
 /** TileTypeProcs definitions for TileType::Road tiles. */

src/saveload/saveload.h

@@ -416,6 +416,7 @@ enum class SaveLoadVersion : uint16_t {
 	BuoysAt0_0, ///< Saveload version: 364, GitHub pull request: 14983\n Allow to build buoys at (0x0).
 
 	DriveBackwards, ///< Saveload version: 365, GitHub pull request: 15379\n Trains can drive backwards.
+	DepotsUnderBridges, ///< Saveload version: 366, GitHub pull request: 15836\n Allow depots under bridges.
 
 	MaxVersion, ///< Highest possible saveload version.
 };

src/water_cmd.cpp

@@ -119,7 +119,12 @@ CommandCost CmdBuildShipDepot(DoCommandFlags flags, TileIndex tile, Axis axis)
 		return CommandCost(STR_ERROR_MUST_BE_BUILT_ON_WATER);
 	}
 
-	if (IsBridgeAbove(tile) || IsBridgeAbove(tile2)) return CommandCost(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
+	for (Tile t : {tile, tile2}) {
+		if (IsBridgeAbove(t)) {
+			int height_diff = GetTileMaxZ(t) + MINIMAL_DEPOT_BRIDGE_HEIGHT - GetBridgeHeight(GetSouthernBridgeEnd(t));
+			if (height_diff > 0) return CommandCostWithParam(STR_ERROR_BRIDGE_TOO_LOW_FOR_SHIP_DEPOT, height_diff * TILE_HEIGHT_STEP);
+		}
+	}
 
 	if (!IsTileFlat(tile) || !IsTileFlat(tile2)) {
 		/* Prevent depots on rapids */
@@ -1000,6 +1005,7 @@ static void DrawTile_Water(TileInfo *ti)
 
 		case WaterTileType::Depot:
 			DrawWaterDepot(ti);
+			DrawBridgeMiddle(ti, BRIDGEPILLARFLAGS_ALL);
 			break;
 	}
 }
@@ -1466,15 +1472,27 @@ static CommandCost TerraformTile_Water(TileIndex tile, DoCommandFlags flags, [[m
 }
 
 /** @copydoc CheckBuildAboveProc */
-static CommandCost CheckBuildAbove_Water(TileIndex tile, DoCommandFlags flags, [[maybe_unused]] Axis axis, int height)
+static CommandCost CheckBuildAbove_Water(TileIndex tile, [[maybe_unused]] DoCommandFlags flags, [[maybe_unused]] Axis axis, int height)
 {
-	if (IsWater(tile) || IsCoast(tile)) return CommandCost();
-	if (IsLock(tile)) {
-		int height_diff = GetTileMaxZ(tile) + GetLockPartMinimalBridgeHeight(GetLockPart(tile)) - height;
-		if (height_diff > 0) return CommandCostWithParam(STR_ERROR_BRIDGE_TOO_LOW_FOR_LOCK, height_diff * TILE_HEIGHT_STEP);
-		return CommandCost{};
+	switch (GetWaterTileType(tile)) {
+		case WaterTileType::Clear:
+		case WaterTileType::Coast:
+			break;
+
+		case WaterTileType::Lock: {
+			int height_diff = GetTileMaxZ(tile) + GetLockPartMinimalBridgeHeight(GetLockPart(tile)) - height;
+			if (height_diff > 0) return CommandCostWithParam(STR_ERROR_BRIDGE_TOO_LOW_FOR_LOCK, height_diff * TILE_HEIGHT_STEP);
+			break;
+		}
+
+		case WaterTileType::Depot: {
+			int height_diff = GetTileMaxZ(tile) + MINIMAL_DEPOT_BRIDGE_HEIGHT - height;
+			if (height_diff > 0) return CommandCostWithParam(STR_ERROR_BRIDGE_TOO_LOW_FOR_SHIP_DEPOT, height_diff * TILE_HEIGHT_STEP);
+			break;
+		}
 	}
-	return Command<Commands::LandscapeClear>::Do(flags, tile);
+
+	return CommandCost();
 }
 
 /** TileTypeProcs definitions for TileType::Water tiles. */